Nowadays, in the context of global warming, there is a growing demand for transportation machines to improve fuel consumption. For in-vehicle electric components to be mounted, in particular, in automobiles, there is an urgent need to further reduce their size and weight. In addition, among the in-vehicle electric components, with respect to rotating electrical machines for vehicle, such as an alternator, attempts have been actively made directed to improvement in power generation efficiency and power conversion efficiency. As one of these, there is an attempt to apply an inverter configuration to a power conversion unit in place of a rectifier or the like. As compared to the rotating electrical machine with a rectifier, the rotating electrical machine with the power conversion unit to which an inverter configuration is applied, is sophisticated in control of its output current, so that it is allowed to add thereto a new function of generating regenerative power, starting engine or the like.
Meanwhile, in the rectifier for in-vehicle apparatus, a diode is used as a power semiconductor element, whereas, in the inverter for in-vehicle apparatus, a MOS-FET (Metal Oxide Semiconductor—Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor) is used. These power semiconductor elements used in the inverter are switching elements that turn on/off (ON-OFF) with voltages applied to their gates, and have a smaller current loss (hereinafter represented as ON-resistance) at the time of gate-on, as compared to the diode. Thus, in the in-vehicle apparatus with the power conversion unit to which an inverter configuration is applied, the power generation efficiency and/or the power conversion efficiency are improved. Further, the switching element such as a MOS-FET or an IGBT is also used in the power semiconductor device for controlling field current in an alternator or a motor generator. The power semiconductor element for controlling the field current is placed in a path through which power is supplied to the field winding of a rotor as a rotator member, and controls the field current.
In-vehicle power semiconductor devices to be mounted in these in-vehicle electric components are conventionally fabricated by incorporating, for example, an encased-type power semiconductor device which is configured by soldering a power semiconductor element on an insulative board with a patterned wiring and making connections using wiring members followed by encapsulating the resultant with a silicone gel or the like, or a mono-functional discrete-type power semiconductor device which is configured by subjecting a diode, MOS-FET or like element to transfer molding. Such a power semiconductor device is placed near a heat dissipater such as a heat sink of the in-vehicle apparatus, so that heat generated by the power semiconductor element is discharged through the heat dissipater.
The power semiconductor device of the in-vehicle electric component is, because of small space for mounting it, required to be downsized. However, in the power semiconductor device which is to be mounted in the in-vehicle electric component and in which a power semiconductor element given as a switching element, such as a MOS-FET or an IGBT, is mounted, current intermittently flows due to switching of the power semiconductor element. As to the power semiconductor device, it is required to provide a capacitor for mitigating voltage variation at the time of switching of the power semiconductor element. The capacitor is required to be placed near the power semiconductor device, and this causes an obstructive factor against downsizing of the rotating electrical machine.
For example, in Patent Document 1, there is disclosed a mold-type semiconductor device in which a chip capacitor is attached to a lead frame at between a power source and the ground, and a low-power integrated circuit (IC chip) and the chip capacitor are encapsulated with a resin. This semiconductor device has a configuration in which the capacitor is mounted on a tie bar of the lead frame and encapsulated with a resin. This allows the capacitor to be mounted near the low-power integrated circuit, as well as achieves noise reduction.